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Fuel cell system comprising battery and method of consuming residual fuel in the fuel cell system

Fuel cell system comprising battery and method of consuming residual fuel in the fuel cell system description/claims

This application claims the benefit of Korean Patent Application No. 2007-49944, filed May 22, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

1. Field of the Invention

Aspects of the present invention relate to an energy generation system to supply power to a load and a method of operating the energy generation system, and more particularly, to a fuel cell system comprising a battery and a method of consuming residual fuel in the fuel cell system.

2. Description of the Related Art

Fuel cell systems are expected to be the next generation energy supply source. A conventional fuel cell system includes a fuel cell in which power is generated; a cartridge in which fuel is stored; a fuel supply apparatus to supply the fuel in the cartridge to the fuel cell; an auxiliary battery; and a control system that controls a process of supplying the fuel, a process of generating power, a process of applying the generated power to a load, and an operation of the auxiliary battery. In such fuel cell system, if there is residual fuel in the fuel cell system when the fuel cell system is separated from a load or when the operation of the fuel cell system is stopped, a cathode potential of the fuel cell may increase due to the residual fuel and the performance of the fuel cell may be greatly decreased. Also, if there is residual fuel in the fuel cell, a catalyst of the fuel cell can be damaged. As a result, the performance of the fuel cell can be decreased.

In order to address problems associated with the residual fuel in the fuel cell system, various methods of consuming the residual fuel have been proposed. One of the methods includes charging a battery using the residual fuel so that the residual fuel is consumed by charging the battery. However, consuming the residual fuel by only charging a battery causes at least the following problems: First, an additional circuit to measure the capacity of the battery is necessary. As a result, the configuration of the fuel cell system is unnecessarily complicated, which makes decreasing the size of the fuel cell system difficult and increases the manufacturing costs. Second, in consideration of the consumption of the residual fuel, the battery must be always maintained at a state of deficient capacity, thus the capacity of the battery for other uses is decreased.

To solve the above and/or other problems, aspects of the present invention provide a fuel cell system that does not require an additional apparatus for consuming residual fuel. Aspects of the present invention also provide a method of consuming the residual fuel in the fuel cell system.

According to an aspect of the present invention, there is provided a fuel cell system comprising a fuel cell, a system controller, a back-up battery, a converter unit, a fuel supply control, and a driver that drives the fuel supply control, wherein a charger is disposed between the converter and a load.

According to an aspect of the present invention, a power output end of the charger may be directly connected to the back-up battery via a switch; the converter unit may comprise a first converter and a second converter, wherein the first converter is connected to the back-up battery and the second converter is connected to the fuel cell, and wherein the first and second converters are commonly connected to the charger; and a switch may be installed between the back-up battery and the first converter and between a power output end of the second converter and the charger.

According to an aspect of the present invention, there is provided a method of consuming residual fuel in a fuel cell system, the method comprising: comparing a first power and a second power; wherein the first power is an output power from the fuel cell and the second power is an intrinsic power consumed by the fuel cell system; driving the fuel cell system in a power loss mode if the first power is less than the second power, and determining whether the back-up battery is completely charged if the first power is greater than the second power; wherein, if the first power is greater than the second power, driving the fuel cell system in a valve OFF driving mode if the back-up battery is completely charged, and driving in a charge mode when the back-up battery is not completely charged; wherein during one of the power loss mode, the charge mode, and the valve OFF driving mode, comparing an output voltage from the fuel cell and a set voltage, and when the output voltage from the fuel cell is greater than the set voltage, returning back to the comparison of the first power and the second power.

According to aspects of the invention, when driving the fuel cell system in the charge mode, if the output voltage from the fuel cell is greater than the set voltage and the first power is less than the second power, the fuel cell system may be driven in the power loss mode.

According to aspects of the invention, when the fuel cell system is driven in the power loss mode, while the fuel supply is stopped, the second converter and the charger may be enabled, the first converter may be disabled, and the driver and the back-up battery may be maintained in an inactive state.

According to aspects of the invention, when the fuel cell system is driven in the charge mode, while the fuel supply is stopped, the first converter and the driver may be maintained in an inactive state, the second converter and the charger may be enabled, and a power output end of the charger and the back-up battery may be electrically connected.

According to aspect of the present invention, the method may further comprising, when the fuel cell system is driven in the valve OFF driving mode, while the fuel supply is stopped, enabling the first and second converters, maintaining the driver in an active state, disabling the charger, maintaining the back-up battery in an active state, and applying an OFF driving signal to the driver.

According to aspects of the invention, one of the first and second converters may be firstly enabled.

According to aspects of the invention, after applying the OFF driving signal to the driver, the method may further comprise: driving the fuel cell system in the charge mode to charge the back-up battery; determining whether the output power from the fuel cell reaches a set power; and disabling the first and second converters and the charger if the output power from the fuel cell reaches the set power, and repeating the driving of the fuel cell system in the charge mode if the output power from the fuel cell does not reach the set power.

According to aspects of the invention, after applying the OFF driving signal to the driver, the method may further comprise: disabling the first converter; determining whether the output power from the fuel cell reaches the set power; and disabling the first and second converters and the charger if the output power from the fuel cell reaches the set power, and enabling the charger and electrically connecting the output end of the charger and the back-up battery if the output power from the fuel cell does not reach the set power.

According to aspects of the invention, the fuel supply control may comprise a valve, and the driver may comprise a valve driver; and a switch may be installed each between the back-up battery and the first converter and between the output end of the second converter and the charger.

According to aspects of the present invention, an external device for consuming residual fuel is not necessary and an additional hardware for realizing a method of consuming the residual fuel is unnecessary. Also, the amount of residual fuel in the fuel cell can be minimized by selectively using the three modes for consuming the residual fuel according to the power output conditions of the fuel cell, thereby preventing the fuel cell from reducing performance due to the residual fuel.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

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